Roofing material has an upper surface intended to be exposed to weather and a lower surface facing in the direction opposite to the upper surface. A typical asphalt shingle has an asphalt-based substrate with granules deposed thereon. The granules are embedded in a layer of asphalt on the upper surface of the substrate, referred to herein as the face coating. The face coating is of sufficient thickness to ensure that the granules are adequately retained on the surface of the shingle. The granules provide weather resistance, fire resistance and/or an aesthetic appearance. The aesthetic appearance may be achieved through pigmentation. Traditionally, No. 11 grade granules having a particle size of about 16-20 US mesh or about 47-33 mils are used in typical asphalt shingles. With increasing costs of petroleum based products, including asphaltic petroleum based products, it is desirable to reduce the asphalt component raw material cost. It is also desirable to reduce the amount of petroleum based products in roofing shingles for environmental purposes. It is further desirable to reduce the weight of roofing materials, for example, to reduce the cost associated with shipping the materials.
U.S. Pat. No. 6,933,007 is directed to roofing materials having increased reflectivity properties. The '007 patent discloses that the roofing materials have multiple coating layers, i.e, more than one layer, each of which has a different granule size, which are used to achieve the increased reflectivity. The '007 patent also discloses that the roofing materials include two granule coating layers with the first coating layer comprising No. 11 grade granules having an average particle size of about 19 US mesh and a second coating layer comprising granules having an average particle size of about 47 or 50 US mesh. In addition, the '007 patent discloses that the roofing materials include two granule coating layers with the first coating layer comprising No. 14 grade granules having an average particle size of about 22 US mesh and a second coating layer comprising granules having an average particle size of about 47 or 50 US mesh. Col. 16, lines 13-50.
Attempts to reduce the cost and/or weight of shingles have met with difficulty in achieving desired physical characteristics, and particularly desired impact resistance. To achieve the desired impact resistance, additional components have been used, such as reinforcing backings, including polypropylene (Capstone™ shingles), Kevlar fabric (U.S. Pat. No. 5,571,596) and web material (U.S. Pat. No. 6,228,785).